title: Comparison of in vitro proliferative capacity of human periodontal ligament cells in juvenile and aged donors.
abstract: OBJECTIVE
  The aim of this study is to compare the in vitro proliferative capacity of periodontal ligament (PDL) cells from aged and juvenile donors.
  
  
  METHODS
  Flow-cytometric analysis of the cell cycle was used to compare the length of each cell cycle, and the ratio of the cells progressing through the cycles between four PDL cells from juvenile donors and four cells from aged donors. Then, replicative capacity of the PDL cells from three juvenile and three aged donors was compared by serial cultures. Finally, expression of c-fos was compared between cells proliferating and cells which had reached senescent.
  
  
  RESULTS
  Flow-cytometric analysis of the cell cycle had revealed that although there were no differences in the length of each phase of the cell cycle, significant differences were found in the ratio of the cells entering from Gap I to DNA synthesis phase of the cell cycle (P < 0.025). Replicative capacity was much longer in two cells from juvenile donors (about 20 population doublings), while all cells from aged donors showed short dividing abilities (less than eight population doublings), hence entered senescent phases shortly. Additionally, no c-fos was detected in cells which had reached senescence upon stimulation with serum.
  
  
  CONCLUSIONS
  It is generally believed that aged humans have an impaired wound healing ability. We believe that more fibrotic PDL tissues seen in aged humans might be the reason for this, and suggest that this phenomena might be due to the progressive accumulation of senescent cell populations.
authors.affiliation: Department of Periodontology and Endodontology, Okayama University Dental School, Japan.
authors.forename: F
authors.initials: F
authors.lastname: Nishimura
authors.forename: V P
authors.initials: VP
authors.lastname: Terranova
authors.forename: M
authors.initials: M
authors.lastname: Braithwaite
authors.forename: R
authors.initials: R
authors.lastname: Orman
authors.forename: H
authors.initials: H
authors.lastname: Ohyama
authors.forename: J
authors.initials: J
authors.lastname: Mineshiba
authors.forename: H H
authors.initials: HH
authors.lastname: Chou
authors.forename: S
authors.initials: S
authors.lastname: Takashiba
authors.forename: Y
authors.initials: Y
authors.lastname: Murayama
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D002453:Cell Cycle; D002455:Cell Division; D002478:Cells, Cultured; D016922:Cellular Senescence; D002648:Child; D005434:Flow Cytometry; D006801:Humans; D008875:Middle Aged; D010513:Periodontal Ligament / Q000166:cytology*; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis; D012038:Regeneration; D018709:Statistics, Nonparametric; D018808:Transcription Factor AP-1 / Q000378:metabolism
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D018808:Transcription Factor AP-1